bibtex: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/bibtex - from package: texlive

You may install the required package with command yum install {package}

Error in other languages:
bibtex: bevel nie gevind nie
bibtex: comandă negăsită
bibtex: comando não encontrado
bibtex: commande introuvable
bibtex: command not found
bibtex: käsku ei ole
bibtex: không tìm thấy lệnh
bibtex: komanda nerasta
bibtex: Kommando nicht gefunden.
bibtex: kommandot finns inte
bibtex: komut yok
bibtex: nie znaleziono polecenia
bibtex: níor aimsíodh an t-ordú
bibtex: no se encontró la orden
bibtex: no s'ha trobat l'ordre
bibtex: opdracht niet gevonden
bibtex: parancs nem található
bibtex: perintah tidak ditemukan
bibtex: príkaz nenájdený
bibtex: příkaz nenalezen
bibtex: команда не найдена
bibtex: командата не е открита
bibtex: 命令找不到
bibtex: コマンドが見つかりません